With ever increasing road traffic levels there is a particular need to evaluate the performance of traffic control systems. One particular traffic control system that is almost universally encountered is signalized intersections. Evaluation of signalized intersection performance may take various forms. One form of particular importance includes the analysis of average stopped delay per vehicle. The Institute of Transportation Engineers (“ITE”) defines stopped delay as the time a vehicle is standing still while waiting in line in the approach to an intersection. The average stopped delay per vehicle for a given intersection approach is the sum of the individual stopped delay divided by the volume of traffic that passes through the intersection approach including vehicles that do not stop.
A basic method for estimating average stopped delay per vehicle suggested by the ITE includes the use of a human observer for counting vehicles. Typically, for fifteen minutes the observer counts the number of vehicles stopped at an intersection approach at fifteen second intervals. The total number of vehicles that passed through the intersection is also recorded. Once the data are collected, the total number of vehicles that were counted as stopped is multiplied by the fifteen second time increment and then divided by the total number of vehicles that passed through the intersection from that approach. This method may be referred to as the ITE manual method.
Although the ITE manual method is common in the field of traffic engineering, it does have several possible error sources. For example, the ITE manual method assumes that vehicles counted as stopped at each fifteen-second interval have been stopped at the intersection for the entire fifteen seconds. Error can also arise from the use of human observers. Long traffic queues can make it difficult for observers to accurately count the stopped vehicles. The difficulties associated with manual analysis do not disappear even if an electronic counter is used to simplify the steps of the ITE manual method.
Consequently, it would be desirable to reduce the large labor cost and reduce the inaccuracies inherent in the ITE manual method. It would further be desirable to provide automated, instead of manual estimation of the average stopped delay per vehicle at a given signalized intersection.